1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive porcelain composition, a piezoelectric/electrostrictive device, and a method of manufacturing a piezoelectric/electrostrictive device.
2. Description of the Related Art
Heretofore, piezoelectric/electrostrictive devices have been known to be capable of controlling micro displacement on the order of sub-microns. Piezoelectric/electrostrictive devices are especially suitable for the control of the micro displacement. In the device, a piezoelectric/electrostrictive body (piezoelectric/electrostrictive portion) formed of a piezoelectric/electrostrictive porcelain composition and an electrode portion to which a voltage is applied are laminated on a substrate made of a ceramic. Additionally, the device has superior characteristics such as a high electromechanical conversion efficiency, a high-speed response, a high durability, and a reduced power consumption. The piezoelectric/electrostrictive device is used in various applications such as a piezoelectric pressure sensor, a probe moving mechanism of a scanning type tunnel microscope, a rectilinear guide mechanism in an ultra-precise working device, a servo valve for hydraulic control, a head of a VTR device, a pixel constituting a flat panel type image display device, and a head of an ink jet printer.
Moreover, the piezoelectric/electrostrictive porcelain composition constituting the piezoelectric/electrostrictive body is also variously investigated. For example, there has been disclosed a Pb(Mg1/3Nb2/3)O3—PbTiO3—PbZrO3 ternary solid solution system composition, or a piezoelectric/electrostrictive porcelain composition in which a part of Pb in the composition is replaced with Sr, La or the like (see, e.g., Japanese Patent Publication No. 44-17103 and Japanese Patent Publication No. 45-8145). As to the piezoelectric/electrostrictive body itself which is the most important portion that determines a piezoelectric/electrostrictive characteristic of the piezoelectric/electrostrictive device, the piezoelectric/electrostrictive device is expected to be obtained which has a superior piezoelectric/electrostrictive characteristic (e.g., piezoelectric d constant).
On the other hand, it is disclosed that when the piezoelectric/electrostrictive body is formed using a piezoelectric/electrostrictive porcelain composition containing as a major component a predetermined PMN-PZ-PT ternary solid solution system composition containing Ni or oxide thereof, it is possible to manufacture a piezoelectric/electrostrictive device which has superior piezoelectric/electrostrictive characteristics and whose linearity of a flexural displacement with respect to an electric field is high up to a high electric field region (see, e.g., Japanese Patent Application Laid-Open No. 2002-217464 and Japanese Patent Application Laid-Open No. 2002-217465).
However, a raw piezoelectric/electrostrictive material needs to be sintered at a high temperature of 1200° C. or more so that the piezoelectric/electrostrictive body is denser, superior in crystallinity, and exhibits high piezoelectric/electrostrictive characteristics. Therefore, in addition to the problem that energy costs are high, there is a problem in that since it is difficult to use an Ag electrode or an Ag—Pd electrode having a comparatively low melting point, an electrode containing expensive Pt has to be used in many cases, and the article lacks in versatility. An element such as Pb or Ni contained in the piezoelectric/electrostrictive porcelain composition is gradually easily evaporated on high-temperature conditions at 1200° C. or more. Therefore, there are problems in that the finally resultant composition of the piezoelectric/electrostrictive body easily deviates from the expected composition, and in that it is difficult to obtain a piezoelectric/electrostrictive body exhibiting the desired piezoelectric/electrostrictive characteristics.